Engine

ABSTRACT

An engine including a main fuel injection valve, a pilot fuel injection valve, a liquid fuel supply rail pipe, and a pilot fuel supply rail pipe. The main fuel injection valve supplies liquid fuel from the liquid fuel supply rail pipe to a combustion chamber during combustion in a diffusion combustion system. The pilot fuel injection valve supplies pilot fuel from the pilot fuel supply rail pipe to the combustion chamber in order to ignite gaseous fuel during combustion in a premixed combustion system. The liquid fuel supply rail pipe is disposed at one side of an imaginary vertical plane (P1) including an axis of a crank shaft. The pilot fuel supply rail pipe is disposed at the side of the imaginary vertical plane at which the liquid fuel supply rail pipe is disposed.

CROSS-REFERENCE

This application is a continuation of a US National Stage Applicationunder 35 U.S.C. § 371, U.S. application Ser. No. 16/316,762 filed Jan.10, 2019, of International Application No. PCT/JP2017/021521 filed Jun.9, 2017, which claims foreign priority of JP2016-139440 filed Jul. 14,2016, the disclosures of which are hereby incorporated by reference intheir entirety.

TECHNICAL FIELD

The present invention relates to an engine employing multiple types offuel. Specifically, the present invention relates to arrangement ofpipes for supplying liquid fuel in an engine.

BACKGROUND ART

A known so-called dual fuel engine is capable of being driven whileselecting one of a premixed combustion system in which fuel gas such asnatural gas is mixed with air for combustion and a diffusion combustionsystem in which liquid fuel (fuel oil) such as heavy oil is diffused forcombustion. Patent Literature 1 (PTL 1) discloses an engine device thatis an engine of this type.

In the engine device of PTL 1, a liquid fuel supply rail pipe forsupplying liquid fuel to combustion chambers during combustion in thediffusion combustion system is disposed at the right of a crank shaftserving as an engine output shaft. On the other hand, a common rail pipefor supplying pilot fuel to the combustion chambers in order to ignitegaseous fuel during combustion in the premixed combustion system isdisposed at the left of the crank shaft and immediately at a side of anexhaust manifold in plan view, specifically, above an exhaust branchpipe of the exhaust manifold.

CITATION LIST Patent Literature

-   PTL 1: Japanese Patent Application Laid-Open No. 2015-86728

SUMMARY OF INVENTION Technical Problem

In the configuration of PTL 1, however, the liquid fuel supply rail pipeis located at the right of the crank shaft and the pilot fuel supplycommon rail pipe is located at the left of the crank shaft. Thus, it isdifficult to perform maintenance of these rail pipes from a commonplace, and this causes a decrease in working efficiency.

Some aspects of the present invention have been made in view of theforegoing circumstances, and have a latent purpose of easing maintenanceof a liquid fuel supply rail pipe and a pilot fuel supply rail pipe.

Solution to Problem and Advantages

Problems to be solved by the invention are as described above, and next,means for solving the problems and advantages thereof will be described.

In an aspect of the invention, an engine having the followingconfiguration is provided. That is, the engine is operable in a premixedcombustion system in which gaseous fuel mixed with air is caused to flowinto combustion chambers and a diffusion combustion system that injectsliquid fuel into the combustion chambers for combustion. The engineincludes a main fuel injection valve, a pilot fuel injection valve, aliquid fuel supply rail pipe, and a pilot fuel supply rail pipe. Themain fuel injection valve supplies liquid fuel to the combustion chamberduring combustion in the diffusion combustion system. The pilot fuelinjection valve supplies pilot fuel to the combustion chamber in orderto ignite gaseous fuel during combustion in the premixed combustionsystem. The liquid fuel supply rail pipe is disposed at one side of animaginary vertical plane including a crank shaft of the engine andsupplies liquid fuel to the main fuel injection valve. The pilot fuelsupply rail pipe is disposed at the side of the imaginary vertical planeat which the liquid fuel supply rail pipe is disposed and supplies pilotfuel to the pilot fuel injection valve. The pilot fuel supply rail pipeis disposed above the liquid fuel supply rail pipe. The liquid fuelsupply rail pipe and the pilot fuel supply rail pipe are disposed in adirection parallel to an axis of the crank shaft.

Accordingly, maintenance of the liquid fuel supply rail pipe andmaintenance of the pilot fuel supply rail pipe can be performed from oneside of the crank shaft of the engine, and thus, maintenance can beperformed easily.

In the engine, an exhaust manifold that collects exhaust air generatedby combustion in the combustion chamber to emit the air to outside ispreferably disposed at a side of the imaginary vertical plane oppositeto the side at which the liquid fuel supply rail pipe is disposed.

Accordingly, the exhaust manifold is disposed at the side of the crankshaft opposite to the side at which the liquid fuel supply rail pipe andthe pilot fuel supply rail pipe are disposed. Thus, in a case where fuelyet to be supplied to the combustion chamber leaks, a risk of fire dueto contact of the fuel with the surface of the high-temperature exhaustmanifold can be eliminated or reduced.

The engine preferably has the configuration as follows. Specifically,the engine further includes a fuel injection pump and a covering member.The fuel injection pump is disposed at the side of the imaginaryvertical plane at which the liquid fuel supply rail pipe is disposed andsupplies fuel to the main fuel injection valve. The covering membercovers the liquid fuel supply rail pipe, the pilot fuel supply railpipe, and the fuel injection pump.

Accordingly, even if fuel leaks from one of the liquid fuel supply railpipe, the pilot fuel supply rail pipe, and the fuel injection pump,scattering of fuel can be prevented or reduced, and thus,maintainability and safety can be enhanced.

The engine preferably has the following configuration. Specifically, theengine includes a pilot fuel supply main pipe, a liquid fuel suppl mainpipe, and a fuel return pipe. Fuel to be sent to the pilot fuel supplyrail pipe flows by way of the pilot fuel supply main pipe. Fuel to besent to the liquid fuel supply rail pipe flows by way of the liquid fuelsupply main pipe. The fuel return pipe returns redundant fuel from afuel injection pump that supplies fuel to the main fuel injection valve.The pilot fuel supply main pipe, the liquid fuel supply main pipe, andthe fuel return pipe extend in a top-bottom direction through a clampmember.

The engine preferably has the following configuration. Specifically, theengine includes an upper stay and a lower stay. The upper stay is fixedto a cylinder head. The lower stay is fixed to a cylinder block, Thepilot fuel supply rail pipe is supported by the upper stay and the lowerstay.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A view schematically illustrating an engine and fuel supply pathsof two systems according to one embodiment of the present disclosure.

FIG. 2 A rear view of the engine.

FIG. 3 A partial rear cross-sectional view illustrating a configurationaround a combustion chamber in detail.

FIG. 4 A front view of the engine.

FIG. 5 A plan view of the engine.

FIG. 6 A right side view of the engine.

FIG. 7 A schematic front perspective view illustrating a liquid fuelsupply path.

FIG. 8 A left side view of the engine.

FIG. 9 A perspective view of the engine illustrating a state where apart of a side cover and a heat shielding cover are detached.

FIG. 10 An enlarged perspective view of the engine illustrating a statein which the side cover is detached.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present disclosure will be described with referenceto the drawings. FIG. 1 is a view schematically illustrating an engine21 and fuel supply paths 30 and 31 of two systems according to oneembodiment of the present disclosure. FIG. 2 is a rear view of theengine 21. FIG. 3 is a partial rear cross-sectional view illustrating aconfiguration around a combustion chamber 110 in detail. FIG. 4 is afront view of the engine 21. FIG. 5 is a plan view of the engine 21.FIG. 6 is a right side view of the engine 21. FIG. 7 is a schematicfront perspective view illustrating a liquid fuel supply path. FIG. 8 isa left side view of the engine 21. FIG. 9 is a perspective view of theengine 21 illustrating a state where a part of a side cover 43 and aheat shielding cover 45 are detached.

The engine (multi-cylinder engine) 21 according to this embodimentillustrated in FIG. 1 is a so-called dual fuel engine operable in both apremixed combustion system in which gaseous fuel mixed with air iscaused to flow into combustion chambers and a diffusion combustionsystem that injects liquid fuel into combustion chambers for combustion.The engine 21 according to this embodiment serves as a driving source ofa propulsive and power generating mechanism of an unillustrated ship andis mounted to an inner bottom plate of an engine room of the ship with abase interposed therebetween.

A crank shaft 24 serving as an engine output shaft projects rearwardfrom a rear end of the engine 21. An unillustrated speed-reducer iscoupled to one end of the crank shaft 24 to enable power transfer. Thespeed reducer is sandwiched between the crank shaft 24 and anunillustrated propeller shaft of the ship, and the propeller shaft isdisposed coaxially with the crank shaft 24. A propeller for generatingpropulsive power of the ship is attached to an end of the propellershaft. The speed-reducer includes a PTO shaft, and an unillustratedshaft-driving power generator is coupled to the PTO shaft to enablepower transfer.

This configuration enables a driving force of the engine 21 to bebranched into the propeller shaft and the shaft-driving power generatorand transferred through the speed-reducer. Accordingly, propulsive powerof the ship is generated, and electric power generated by driving of theshaft-driving power generator is supplied to electric circuits in theship.

Next, the engine 21 will be described in detail with reference to thedrawings. The engine 21 is a dual fuel engine as described above, andcan be driven while selecting one of a premixed combustion system inwhich fuel gas such as natural gas is mixed with the air for combustionand a diffusion combustion system in which liquid fuel (fuel oil) suchas heavy oil is diffused for combustion.

Positional relationship among the front, rear, left, and right in theconfiguration of the engine 21 will be described below with a sideconnected to the speed-reducer (a side where a flywheel is disposed)being defined as rear, a right side toward the front surface of theengine 21 being defined as right, a let side toward the front surface ofthe engine 21 being defined as left. Thus, the front-rear direction(longitudinal direction) can be a direction parallel to the axis of thecrank shaft 24, and the left-right direction (lateral direction) can bea direction perpendicular to the axis of the crank shaft 24. It shouldbe noted that this description is not intended to limit the orientationof the engine 21, and the engine 21 can be placed in variousorientations in accordance with application and others.

As illustrated in FIG. 1, the fuel supply paths of two systems 30 and 31are connected to the engine 21. A gaseous fuel tank 32 for storingliquefied natural gas (LNG) is connected to one fuel supply path 30,whereas a liquid fuel tank 33 for storing marine diesel oil (MDO) isconnected to the other fuel supply path 31. In this configuration, thefuel supply path 30 supplies fuel gas to the engine 21, and the fuelsupply path 31 supplies fuel oil to the engine 21.

In the fuel supply path 30, a gaseous fuel tank 32 that stores gaseousfuel in a liquefied state, a vaporizing device 34 that vaporizes theliquefied fuel in the gaseous fuel tank 32, and a gas valve unit 35 thatadjusts the supply rate of fuel gas from the vaporizing device 34 to theengine 21, are arranged in this order from the upstream side.

As illustrated in FIGS. 2 through 4, the engine 21 is an in-linemulti-cylinder engine configured by mounting cylinder heads 26 onto acylinder block 25. The crank shaft 24 is rotatably supported on a lowerportion of the cylinder block 25 with an axis 24 c oriented in thefront-rear direction as illustrated FIGS. 2 and 4.

In the cylinder block 25, a plurality of (six in this embodiment)cylinders are arranged in a line (in series) along the axis of the crankshaft 24. As illustrated in FIG. 3, each cylinder houses a piston 78such that the pistons 78 are slidable in the top-bottom direction. Thispiston 78 is coupled to the crank shaft 24 through an unillustrated rod.

As illustrated in FIGS. 5 and 6, the plurality of (six in thisembodiment) cylinder heads 26 are attached to the cylinder block 25 tocover the cylinders individually from above. The cylinder heads 26 areprovided to the individual cylinders, and are fixed to the cylinderblock 25 using head bolts 99. As illustrated in FIG. 3, in eachcylinder, the combustion chamber 110 is defined in space surrounded bythe upper surface of the piston 78 and the cylinder head 26.

As illustrated in FIG. 5, a plurality of head covers 40 correspond tothe individual cylinders and are arranged on the cylinder heads 26 in aline along the direction of the axis 24 c of the crank shaft 24(front-rear direction). As illustrated in FIG. 3, each of the headcovers 40 houses a valve mechanism constituted by a push rod, a rockerarm, and so forth in order to operate an intake valve and an exhaustvalve. In a state where the intake valves are open, intake air from anintake manifold 67 can be taken in the combustion chambers 110. In astate where the exhaust valves are open, exhaust air from the combustionchambers 110 can be emitted to an exhaust manifold 44.

As illustrated in FIG. 3, the upper end of a pilot fuel injection valve82 described later is disposed near the left of each head cover 40. Withrespect to an imaginary vertical plane P1 (see FIG. 7) including theaxis 24 c of the crank shaft 24, the pilot fuel injection valves 82 areinserted in the cylinder heads 26 from one side (from the left in thisembodiment) of the imaginary vertical plane P1 and extend obliquelydownward toward the combustion chambers 110.

In the following description, a location at one side/the other side ofthe imaginary vertical plane P1 including the axis 24 c of the crankshaft 24 will be sometimes referred to as a location at one side/theother side of the crank shaft 24. The imaginary vertical plane P1 can bean infinite plane in both the direction of the axis 24 c of the crankshaft 24 and the top-bottom direction, but FIG. 7 shows only a part ofthe imaginary vertical plane P1 near the engine 21 for convenience ofexpression in the perspective view.

As illustrated in FIGS. 2, 3, 8, a gas manifold 41 for distributing andsupplying gaseous fuel to the combustion chambers 110 of the cylindersduring combustion in the premixed combustion system is provided at theleft of the cylinder heads 26. The gas manifold 41 extends in thefront-rear direction along the left side surfaces of the cylinder heads26. The plurality of (six in this embodiment) gas branch pipes 41 acorresponding to the combustion chambers 110 of the cylinders areconnected to the gas manifold 41, and as illustrated in FIG. 3, gasinjectors 98 for injecting gaseous fuel are provided at the front endsof the gas branch pipes 41 a. The front ends of the gas injectors 98face intake branch pipes 67 a corresponding to the cylinders and formedinside the cylinder heads 26. By injecting gaseous fuel from the gasinjectors 98, the gaseous fuel can be supplied to the intake branchpipes 67 a of the intake manifold 67.

As illustrated in FIGS. 3, 7, and 9, a liquid fuel supply rail pipe 42for distributing and supplying liquid fuel to the combustion chambers110 of the cylinders during combustion in the diffusion combustionsystem is disposed at the right of the cylinder block 25. The liquidfuel supply rail pipe 42 extends in the front-rear direction along theright side surface of the cylinder block 25. Liquid fuel supplied to theliquid fuel supply rail pipe 42 is distributed and supplied to fuelinjection pumps 89 corresponding to the cylinders. As illustrated inFIG. 3, each cylinder is provided with a main fuel injection valve 79that injects liquid fuel supplied from the fuel injection pump 89. Themain fuel injection valves 79 are inserted in the cylinder heads 26vertically from above the cylinder heads 26, the upper ends of the mainfuel injection valves 79 are disposed inside the head covers 40, and thelower ends of the main fuel injection valves 79 face the combustionchambers 110 of the cylinders. The fuel injection pumps 89 and the mainfuel injection valves 79 are connected to each other through liquid fuelsupply paths 106 formed in the cylinder heads 26.

A liquid fuel return aggregate pipe 48 for collecting redundant fuelreturned from the fuel injection pumps 89 is disposed near the bottom ofthe liquid fuel supply rail pipe 42. The liquid fuel return aggregatepipe 48 is disposed in parallel with the liquid fuel supply rail pipe42, and connected to the fuel injection pumps 89. A fuel return pipe 115for returning liquid fuel to the liquid fuel tank 33 is connected to anend of the liquid fuel return aggregate pipe 48.

As illustrated in FIGS. 3, 7 and 9, a pilot fuel supply rail pipe (pilotfuel supply common rail pipe) 47 for distributing and supplying pilotfuel to the combustion chambers 110 of the cylinders in order to ignitegaseous fuel during combustion in the premixed combustion system isdisposed at the right of the cylinder block 25 and above the liquid fuelsupply rail pipe 42. The pilot fuel supply rail pipe 47 extends in thefront-rear direction along the right side surface of the cylinder block25. As illustrated in FIGS. 3 and 7, the cylinders are provided with thepilot fuel injection valves 82 for injecting liquid fuel (pilot fuel)supplied from the pilot fuel supply rail pipe 47. The pilot fuelinjection valves 82 are inserted in the cylinder heads 26 verticallyfrom above the cylinder heads 26, the upper ends of the pilot fuelinjection valves 82 are disposed immediately at the left side of thehead covers 40, and the lower ends of the pilot fuel injection valves 82face the combustion chambers 110 of the cylinders. As illustrated inFIG. 7, pilot fuel branch pipes 109 corresponding to the cylindersbranch off from the pilot fuel supply rail pipe 47. The pilot fuelbranch pipes 109 pass between the head covers 40 arranged side by side,and are connected to the upper ends of the pilot fuel injection valves82. The pilot fuel branch pipes 109 are covered with a branch pipe cover105 for preventing leaked fuel from scattering.

As illustrated in FIGS. 3, 7, and 9, a step is formed on an upperportion of the right side surface of the engine 21 constituted by thecylinder block 25 and the cylinder heads 26. The pilot fuel supply railpipe 47, the liquid fuel supply rail pipe 42, and the fuel injectionpumps 89 are disposed on this step. A side cover 43 is attached to thecylinder block 25 and the cylinder heads 26 to cover the step. The pilotfuel supply rail pipe 47, the liquid fuel supply rail pipe 42, and thefuel injection pumps 89 are covered with the side cover 43. FIG. 9illustrates a state where a part of the side cover 43 is detached.

As illustrated in FIGS. 2, 3, and 9, the exhaust manifold 44 forcollecting exhaust air generated by combustion in the combustionchambers 110 of the cylinders and emitting the exhaust air to theoutside is disposed in parallel with the gas manifold 41 above the leftof cylinder heads 26 and above the gas manifold 41. The outer peripheryof the exhaust manifold 44 is covered with a heat shielding cover 45(where the heat shielding cover 45 is detached in FIG. 9). Asillustrated in FIG. 3, exhaust branch pipes 44 a corresponding to thecylinders are connected to the exhaust manifold 44. The exhaust branchpipes 44 a communicate with the combustion chambers 110 of thecylinders.

The intake manifold 67 for distributing and supplying outside air(intake air) to the combustion chambers 110 of the cylinders is disposedin parallel with the gas manifold 41 inside the cylinder block 25 andnear the left of the cylinder block 25. As illustrated in FIG. 3, thesix intake branch pipes 67 a branching off from the intake manifold 67are formed inside the cylinder heads 26 and communicate with theindividual combustion chambers 110.

With this configuration, in combustion in the diffusion combustionsystem, an appropriate amount of liquid fuel is injected from the mainfuel injection valves 79 into the combustion chambers 110 at anappropriate timing when air supplied to the cylinders from the intakemanifold 67 is compressed by sliding of the pistons 78. Injection ofliquid fuel into the combustion chambers 110 causes the pistons 78 toreciprocate in the cylinders with propulsive power obtained bycombustion in the combustion chambers 110, and the reciprocatingmovement of the pistons 78 is converted to rotation movement of thecrank shaft 24 through a rod, thereby obtaining a driving force.

On the other hand, in combustion in the premixed combustion system,gaseous fuel from the gas manifold 41 is injected from the gas injectors98 into the intake branch pipes 67 a so that air supplied from theintake manifold 67 and the gaseous fuel are mixed. At an appropriatetiming when the air mixture of the air introduced into the cylinders andthe gaseous fuel is compressed by sliding of the pistons 78, a smallamount of pilot fuel is injected from the pilot fuel injection valves 82into the combustion chambers 110 so that the gaseous fuel is ignited.The pistons 78 reciprocates in the cylinders with propulsive powerobtained by combustion in the combustion chambers 110, and thereciprocating movement of the pistons 78 is converted to rotationmovement of the crank shaft 24 through the rod, thereby obtaining adriving force.

In either case of combustion in the diffusion combustion system andcombustion in the premixed combustion system, exhaust air generated bycombustion is pushed out from the cylinders by movement of the pistons78, and collected in the exhaust manifold 44, and then emitted to theoutside.

As illustrated in FIG. 4, a cooling water pump 53, a lubricating oilpump 55, and a fuel high-pressure pump 56 are disposed at the front endsurface (front surface) of the engine 21 and surround a front endportion of the crank shaft 24. The fuel high-pressure pump 56 isdisposed near the left of the crank shaft 24. A front end portion of theengine 21 is provided with an unillustrated rotation transfer mechanismthat transfers a rotative force of the crank shaft 24. Accordingly, arotative force of the crank shaft 24 is transferred through the rotationtransfer mechanism so that the cooling water pump 53, the lubricatingoil pump 55, and the fuel high-pressure pump 56 provided at the outerperiphery of the crank shaft 24 are thereby driven.

As illustrated in FIG. 8, a lubricating oil cooler 58 and a lubricatingoil strainer 59 are attached to the left side surface of the cylinderblock 25. Lubricating oil supplied from the lubricating oil pump 55 iscooled by the lubricating oil cooler 58, then purified by thelubricating oil strainer 59, and supplied to components of the engine21.

Cooling water sent from the cooling water pump 53 illustrated in FIG. 4cools cylinders of the engine 21, and then is collected to anover-cylinder head cooling water pipe 46 illustrated in, for example,FIG. 5.

The intercooler 51 is disposed along the front end of the engine 21, andcools air compressed by a compressor of the turbocharger 49. Asillustrated in FIG. 8, a cylinder block left cooling water pipe 60extends rearward from ahead of the cylinder block 25 along the gasmanifold 41 to a position between the lubricating oil cooler 58 and thelubricating oil strainer 59, and supplies cooling water to thelubricating oil cooler 58.

As illustrated in FIGS. 5 and 9, the over-cylinder head cooling waterpipe 46 is disposed in parallel with the exhaust manifold 44 and locatedbetween a plurality of head covers 40 located above the cylinder heads26 and the exhaust manifold 44. The over-cylinder head cooling waterpipe 46 is coupled to cooling water branch pipes corresponding to thecylinders, and is connected to cooling water channels of the cylinders(cooling water channels formed in the cylinder heads 26) through thecooling water branch pipes.

The fuel high-pressure pump 56 illustrated in FIG. 4 is driven to rotateto thereby increase the pressure of fuel oil (liquid fuel) supplied fromthe liquid fuel tank 33 illustrated in FIG. 1 through a fuel feed pump166, and sends the fuel oil to the pilot fuel supply rail pipe 47 by wayof the pilot fuel supply main pipe 107 illustrated in, for example, FIG.7. A pilot fuel filter for filtering fuel oil is provided in anintermediate portion of a fuel path from the liquid fuel tank 33 to thefuel high-pressure pump 56.

The fuel feed pump 165 illustrated in FIG. 1 is driven by a motor sothat the fuel feed pump 165 sucks fuel oil from the liquid fuel tank 33and sends the oil to the liquid fuel supply rail pipe 42 by way of theliquid fuel supply main pipe 108 illustrated in, for example, FIG. 7. Amain fuel filter for filtering fuel oil is disposed in an intermediateportion of a supply path of fuel oil from the liquid fuel tank 33 to theliquid fuel supply rail pipe 42.

As illustrated in FIG. 7, the pilot fuel supply main pipe 107, theliquid fuel supply main pipe 108, and the fuel return pipe 115 aredisposed immediately ahead of the cylinder block 25 and extend along theright side surface of the cylinder block 25. The pilot fuel supply mainpipe 107, the liquid fuel supply main pipe 108, and the fuel return pipe115 extend in the top-bottom direction along the right side surface ofthe cylinder block 25 through a plurality of clamp members 111projecting rightward from the front end surface of the cylinder block25.

An engine-side operation control device 71 for performing control suchas start and stopping of the engine 21 is disposed toward the right andahead of the cylinder heads 26, more specifically, on the right sidesurface of the intercooler 51 with a stay interposed therebetween (seeFIGS. 6 and 9). The engine-side operation control device 71 includes anoperation section such as a switch that accepts start and stopping ofthe engine 21 by an operator, and a display that displays an operatingstate of the engine 21. The operator operates the engine-side operationcontrol device 71 to thereby drive the engine 21 in one of the premixedcombustion system and the diffusion combustion system.

Next, arrangement of pipes for supplying liquid fuel in the engine 21will be described more specifically with reference to mainly FIG. 7.

The liquid fuel supply path for supplying liquid fuel to the combustionchambers 110 during combustion in the diffusion combustion system isconstituted by including the liquid fuel supply main pipe 108 and theliquid fuel supply rail pipe 42, for example, as described above. Themain fuel filter is provided in an intermediate portion of the liquidfuel supply main pipe 108. The main fuel filter is disposed near theright of the front end surface of the engine 21. The liquid fuel supplymain pipe 108 extends in the top-bottom direction along the right sidesurface of the cylinder block 25 with interposition of the plurality ofclamp members 111 projecting rightward from the front end surface of thecylinder block 25. The liquid fuel supply rail pipe 42 is connected to adownstream side of the liquid fuel supply main pipe 108. The liquid fuelsupply rail pipe 42 is covered with the side cover 43 while extending inthe front-rear direction along the right side surface of the cylinderblock 25.

Liquid fuel pumped to the liquid fuel supply rail pipe 42 from the fuelfeed pump 165 by way of the liquid fuel supply main pipe 108 isdistributed to the fuel injection pumps 89 corresponding to thecylinders. The fuel injection pumps 89 are covered with the side cover43. As illustrated in FIG. 3, the liquid fuel supplied to the fuelinjection pumps 89 is supplied to the main fuel injection valves 79 byway of the liquid fuel supply paths 106 formed inside the cylinder heads26.

In this manner, the liquid fuel supply path for supplying liquid fuel tothe combustion chambers 110 during combustion in the diffusioncombustion system is disposed at the right of the crank shaft 24 (at theright of the imaginary vertical plane P1 including the axis 24 c of thecrank shaft 24) as a whole. Accordingly, the operator can access theliquid fuel supply path from the right side surface of the engine 21 andperforms maintenance of the liquid fuel supply main pipe 108, the liquidfuel supply rail pipe 42, and the main fuel filter, for example, at atime. In particular, the right side surface of the engine 21 is a sideon which the engine-side operation control device 71 is disposed in atypical configuration, and can be easily accessed by the operator.

The pilot fuel supply path for supplying pilot fuel to the combustionchambers 110 in order to ignite gaseous fuel during combustion in thediffusion combustion system is constituted by including pilot fuelsupply main pipe 107 and the pilot fuel supply rail pipe 47, forexample, as described above. An upstream side of the pilot fuel supplymain pipe 107 is connected to the fuel high-pressure pump 56. Anupstream side of the fuel high-pressure pump 56 is connected to a fuelpath, and an intermediate portion of the fuel path is provided with thepilot fuel filter. An upstream side of this fuel path is connected tothe liquid fuel tank 33. The fuel high-pressure pump 56 and the pilotfuel filter are disposed near the right of the front end surface of theengine 21. The pilot fuel supply main pipe 107 extends in the top-bottomdirection along the right side surface of the cylinder block 25 withinterposition of the clamp members 111 used for supporting the liquidfuel supply main pipe 108. In this manner, the pilot fuel supply mainpipe 107 and the liquid fuel supply main pipe 108 are supported by thecommon clamp members 111, and thus, the number of components can bereduced.

The pilot fuel supply rail pipe 47 is connected to a downstream side ofthe pilot fuel supply main pipe 107. The pilot fuel supply rail pipe 47is covered with the side cover 43 while extending in the front-reardirection along the right side surface of the cylinder block 25.

After being filtered with the pilot fuel filter, pilot fuel pumped tothe pilot fuel supply rail pipe 47 from the fuel high-pressure pump 56by way of the pilot fuel supply main pipe 107 is distributed to thepilot fuel branch pipes 109 corresponding to the cylinders. The pilotfuel branch pipes 109 pass through space between adjacent head covers40. Although not shown in FIG. 7, the pilot fuel branch pipes 109 arecovered with the branch pipe cover 105 from above. The pilot fuelsupplied to the pilot fuel branch pipes 109 is injected at anappropriate timing from the pilot fuel injection valves 82 disposed atthe front end of the downstream side of the pilot fuel branch pipes 109.

In this manner, the pilot fuel supply path for supplying pilot fuel tothe combustion chambers 110 during combustion in the premixed combustionsystem is disposed at the right of the crank shaft 24 (at the right ofthe imaginary vertical plane P1 including the axis 24 c of the crankshaft 24) as a whole in a manner similar to the liquid fuel supply pathdescribed above (see FIG. 7). Accordingly, the operator can easilyaccess the pilot fuel supply path from the right side surface of theengine 21 and easily perform maintenance of the pilot fuel supply mainpipe 107, the pilot fuel supply rail pipe 47, the pilot fuel filter, andso forth at a time. In this manner, maintenance concerning the liquidfuel supply path (including the pilot fuel supply path) can be performedfrom the side surface at one side of the engine 21 at a time, and alayout that eases maintenance by the operator can be obtained.

In a conventional dual fuel engine, the pilot fuel supply rail pipe 47is disposed not inside the side cover 43 but immediately at a side ofthe exhaust manifold 44 in plan view, more specifically, is exposed at aposition above the exhaust branch pipes 44 a of the exhaust manifold 44.The pilot fuel supply rail pipe 47 is generally long, and a joint or thelike is present in the middle of the pipe. Thus, fuel can leak from thisjoint so that the fuel might adhere to the exhaust branch pipes 44 a ofthe exhaust manifold 44. Since high-temperature exhaust air flows insidethe exhaust manifold 44, adhesion of fuel to the exhaust branch pipes 44a at high temperature as described above or other components is notfavorable.

In this regard, in this embodiment, the pilot fuel supply rail pipe 47is disposed at a side of the crank shaft 24 opposite to the exhaustmanifold 44, and is located away from the exhaust manifold 44.Accordingly, even if fuel leaks from a joint or the like of the pilotfuel supply rail pipe 47, the fuel does not adhere to the surface of thehigh-temperature exhaust manifold 44, and the risk of fire can beeliminated or reduced.

In addition, since the pilot fuel supply rail pipe 47 according to thisembodiment is disposed inside the side cover 43, even if fuel leaks froma joint or the like of the pilot fuel supply rail pipe 47, the fuel isnot spattered and maintenance of the engine 21 can be easily performed.

Next, a configuration for supporting the liquid fuel supply rail pipe 42will be described with reference to FIG. 10. FIG. 10 is an enlargedperspective view of the engine 21 illustrating a state where the sidecover 43 is detached.

As illustrated in FIG. 10, the liquid fuel supply rail pipe 42 includesbranching joints 92 disposed at a longitudinally intermediate portionthereof. One branching joint 92 is provided for two cylinders, and twopilot fuel branch pipes 109 are connected to an upper portion of eachbranching joint 92.

As described above, the step is formed on the cylinder block 25 and thecylinder heads 26, and lower stays 95 each having a flat plate shape arefixed to the cylinder block 25 to project upward from the bottom surfaceof this step. L-shaped upper stays 96 are fixed to the cylinder heads 26to project sideways from a side wall of the step. The lower stays 95 andthe upper stays 96 are fixed to the cylinder block 25 or the cylinderheads 26 through bolts and nuts.

Intermediate stays 97 each having a flat plate shape are disposed toconnect the lower stays 95 and the upper stays 96 to each other. Lowerportions of the intermediate stays 97 are fixed to the lower stays 95,and upper portions of the intermediate stays 97 are fixed to the upperstays 96. The branching joints 92 are fixed to the intermediate stays97. These fixings are achieved through bolts and nuts.

In the manner described above, the pilot fuel supply rail pipe 47 issupported using the lower stays 95 and the upper stays 96 from above andbelow (i.e., from both the cylinder block 25 and the cylinder heads 26).Accordingly, rigidity of the support structure can be enhanced, andthus, and vibrations of the pilot fuel supply rail pipe 47 can bereduced.

As described above, the engine 21 according to this embodiment isoperable in the premixed combustion system in which gaseous fuel mixedwith air is caused to flow into the combustion chambers 110 and thediffusion combustion system that injects liquid fuel into the combustionchambers 110 for combustion. The engine 21 includes the main fuelinjection valves 79, the pilot fuel injection valves 82, the liquid fuelsupply rail pipe 42, and the pilot fuel supply rail pipe 47. The mainfuel injection valves 79 supplies liquid fuel to the combustion chambers110 during combustion in the diffusion combustion system. The pilot fuelinjection valves 82 supply pilot fuel to the combustion chambers 110 inorder to ignite gaseous fuel during combustion in the premixedcombustion system. The liquid fuel supply rail pipe 42 is disposed atone side (right side) of the imaginary vertical plane P1 including thecrank shaft 24 of the engine 21 and supplies liquid fuel to the mainfuel injection valves 79. The pilot fuel supply rail pipe 47 is disposedas the same side of the imaginary vertical plane P1 as the liquid fuelsupply rail pipe 42, and supplies pilot fuel to the pilot fuel injectionvalves 82.

Accordingly, maintenance of the liquid fuel supply rail pipe 42 andmaintenance of the pilot fuel supply rail pipe 47 can be performed fromone side (from the right side surface in this embodiment) of the crankshaft 24 of the engine 21, and thus, maintenance can be performedeasily.

The engine 21 according to this embodiment further includes the exhaustmanifold 44 that is disposed at the side (left side) of the imaginaryvertical plane P1 opposite to the liquid fuel supply rail pipe 42,collects exhaust air generated by combustion in the combustion chambers110, and emits the air to the outside.

Accordingly, the exhaust manifold 44 is disposed at the side of thecrank shaft 24 opposite to the side at which the liquid fuel supply railpipe 42 and the pilot fuel supply rail pipe 47 are disposed.Accordingly, it is possible to prevent or reduce an adverse effect onperformance of the engine by fuel yet to be supplied to the combustionchambers 110 at high temperature under the influence of exhaust airflowing in the exhaust manifold 44.

The engine 21 according to this embodiment further includes the fuelinjection pumps 89 and the side cover 43 serving as a covering member.The fuel injection pumps 89 are disposed at the same side (right side)of the imaginary vertical plane P1 as the liquid fuel supply rail pipe42, and supplies fuel to the main fuel injection valves 79. The sidecover 43 covers the liquid fuel supply rail pipe 42, the pilot fuelsupply rail pipe 47, and the fuel injection pumps 89.

Accordingly, even if fuel leaks from one of the liquid fuel supply railpipe 42, the pilot fuel supply rail pipe 47, and the fuel injectionpumps 89, scattering of fuel can be prevented or reduced, and thus,maintainability and safety can be enhanced.

The foregoing description is directed to the preferred embodiment of thepresent invention, and the configuration described above may be changed,for example, as follows.

In the embodiment described above, the engine 21 is used as a drivingsource of a propulsive and power generating mechanism of a ship, butthis is not restrictive, and the engine 21 may be a driving source usedfor other purposes.

In the embodiment described above, the liquid fuel supply rail pipe 42,the pilot fuel supply rail pipe 47, and the fuel injection pumps 89 aredisposed along the right side surface of the engine 21, but this is notrestrictive. Alternatively, the liquid fuel supply rail pipe 42, thepilot fuel supply rail pipe 47, and the fuel injection pumps 89 may bedisposed along the left side surface of the engine 21.

REFERENCE SIGNS LIST

-   -   21 engine    -   24 crank shaft    -   42 liquid fuel supply rail pipe    -   43 side cover (covering member)    -   44 exhaust manifold    -   heat shielding cover    -   47 pilot fuel supply rail pipe    -   79 main fuel injection valve    -   82 pilot fuel injection valve    -   89 fuel injection pump    -   110 combustion chamber    -   P1 imaginary vertical plane

1-3. (canceled)
 4. An engine operable in a premixed combustion system inwhich gaseous fuel mixed with air is caused to flow into a combustionchamber and a diffusion combustion system that injects liquid fuel intothe combustion chamber for combustion, the engine comprising: a mainfuel injection valve configured to supply liquid fuel to the combustionchamber during combustion in the diffusion combustion system; a pilotfuel injection valve configured to supply pilot fuel to the combustionchamber in order to ignite gaseous fuel during combustion in thepremixed combustion system; a liquid fuel supply rail pipe that isconfigured to supply liquid fuel to the main fuel injection valve; apilot fuel supply rail pipe that is configured to supply pilot fuel tothe pilot fuel injection valve; and an exhaust manifold that collectsexhaust air generated by combustion in the combustion chamber anddischarges the air to outside, wherein the liquid fuel supply rail pipeand the pilot fuel supply rail pipe are provided at a position lowerthan the exhaust manifold.
 5. The engine according to claim 4, furthercomprising: a fuel injection pump that is configured to supply liquidfuel from the liquid fuel supply rail pipe to the main fuel injectionvalve, wherein the liquid fuel supply rail pipe and the pilot fuelsupply rail pipe are provided at positions overlapping with the fuelinjection pump in a side view of the engine.
 6. The engine according toclaim 4, further comprising: a covering member that covers the liquidfuel supply rail pipe and the pilot fuel supply rail pipe.